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The existing asymmetric synthesis of enantiopure α-substituted cyclic ethers predominantly relies on the enantioselective C–C bond formation involving a prochiral oxocarbenium ion intermediate. In such a strategy, enantioselectivity and efficiency are typically susceptible to the electronic and substituent effects of either nucleophile or electrophile partners. Here, we describe a strategically different redox deracemization of α-substituted 1,3,4,9-tetrahydropyrano[3,4-b]indoles. This method exhibits good compatibility with the regional variation of the electronic or substituent effect of substrates, thus providing a practical and efficient supplement to the traditional strategy. [ABSTRACT FROM AUTHOR]

The first redox deracemization of a series of cyclic benzylic ethers, including 6 H-benzo[ c]chromenes, isochromans, and 1 H-isochromenes, is described. An 'acetal pool' strategy was adopted to harmonize the complete oxidation of secondary ethers with imidodiphosphoric acid catalyzed asymmetric transfer hydrogenation. The synthetic utility of the process was demonstrated by the effective deracemization of biologically active molecules of interest that are difficult to prepare by other methods. [ABSTRACT FROM AUTHOR]

The first redox deracemization of a series of cyclic benzylic ethers, including 6 H-benzo[ c]chromenes, isochromans, and 1 H-isochromenes, is described. An 'acetal pool' strategy was adopted to harmonize the complete oxidation of secondary ethers with imidodiphosphoric acid catalyzed asymmetric transfer hydrogenation. The synthetic utility of the process was demonstrated by the effective deracemization of biologically active molecules of interest that are difficult to prepare by other methods. [ABSTRACT FROM AUTHOR]